Power bank



FIG. 1 is a perspective view of a power bank showing the claimed design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a rear elevational view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a front elevational view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines illustrate portions of the power bank that form no partof the claimed design.

CLAIM The ornamental design for a power bank, as shown and described.